In the manufacture of different types of light bulbs, various designs have been proposed for integrating bulb control circuitry into the manufacturing process so that the circuitry ultimately is located within the bulb itself and provides one or more lamp control functions when the bulb is connected into a mating electrical socket. One such design is disclosed, for example, in U.S. Pat. No. 4,644,226 issued to Vernooij et al and incorporated herein by reference.
One disadvantage of the Vernooij et al type of bulb construction method is that the semiconductor control circuitry used to control light bulb operation is mounted within and adjacent to the screw shell base or sleeve of the bulb. This location within the light bulb is not particularly well suited for providing good thermal conductivity and heat transfer away from the control circuitry in order to maximize the overall cooling for the bulb. That is to say, the disclosed control circuitry is positioned within the shell base and so confined therein such that all of the heat generated during control circuit operation is largely confined to the interior of the bulb proper and adds to the heat which is already generated by the other active components therein. The additional heat generated by this integrated control circuitry can be considerable in view of the fact that the thyristor of the circuit alone is capable of generating one watt per ampere of thermal heat.
In addition to the above disadvantage associated with bulb over-heating, the manufacturing process of Vernooij et al requires that the control circuitry therein be installed within the light bulb during the high temperature processing thereof where the bulb shell base or sleeve member is subjected to elevated temperatures on the order of 800.degree. C or greater. The exposure of this control circuitry and semiconductor devices connected therein to these high temperature bulb processing steps has a degrading effect on circuit performance as is well known. Furthermore, the necessity for incorporating the semiconductor control circuitry into the shell base and associated glass end piece and center terminal attachment process further complicates the otherwise standard bulb manufacturing process by adding several additional control circuit mounting and bonding steps to the process during the above high temperature processing therefor.